PVDF (polyvinylidene fluoride) resin has excellent chemical stability, resistance to high-strength, weather resistance, ultraviolet resistance, electrical insulation, non-hygroscopicity and self-extinguishing. In order to make PVDF to be more suitably used under more stringent conditions, it is necessary to improve the properties of the PVDF homopolymer such as transparency and flexibility. After PVDF is modified by introducing tetrafluoroethylene and perfluorinated dioxole monomers, the amorphous fluorocarbon resin is formed, which not only has the same properties as that of vinylidene fluoride, but also has characteristics of good transparency, flexibility and solubility, etc. The amorphous fluorocarbon resin is widely used for lenses and other optical apparatus, used as a special film for solar panels, piezoelectric and capacitive application, used as a fuel cell membrane, a transparent and tough coating, used for large-sized blown objects, and so on.
CN102083873A discloses vinylidene fluoride/2,3,3,3-tetrafluoropropene copolymers. The copolymers have excellent optical properties, corrosion resistance and electrical properties, and very low haze. Although the final product of thin film is transparent, there still exists certain haze prohibiting its widespread use.
U.S. Pat. No. 5,140,082 discloses a vinylidenefluoride-trifluoromethylethylene copolymer (3,3,3-trifluoropropene) (TFP). The copolymer is synthesized by bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization, wherein all the TFP is in the initial charge. This copolymer has excellent weathering resistance, corrosion resistance, and electrical characteristics. However, the invention does not relate to the optical transparency of the copolymer.
CN 102161724B discloses a quinary polymerization fluororesin with high transparency and a synthesis method and application thereof. The fluororesin is prepared by copolymerizing the following monomers, 30-45% of ethylene, 40-50% of tetrafluoroethylene, 1-7% of vinyl fluoride, 2-10% of vinylidene fluoride, 3-15% of chlorotrifluoroethylene, based on the mole percent in the copolymer. However, this resin has a melting point of 240-280° C., and thus has higher requirements on the processing equipment, and has a narrow melt processing temperature, thereby having influenceon its application.